International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

Which of the following describes the electronic configuration of potassium?

1. 2, 8, 8, 2

2. 2, 8, 8, 1

3. 2, 7, 2

4. 2, 8, 1

The correct answer is: 2, 8, 8, 1

The correct electronic configuration for potassium, which has an atomic number of 19, is represented as 2, 8, 8, 1. This configuration reflects how many electrons are in each energy level surrounding the nucleus of the atom. Potassium's first energy level can hold up to 2 electrons, which is full with 2 electrons. The second energy level can hold up to 8 electrons, and potassium has 8 electrons in this level. The third energy level can also accommodate a maximum of 8 electrons, and potassium similarly has 8 electrons here. However, it has one additional electron in the fourth energy level, giving the configuration 2 for the first level, 8 for the second, another 8 for the third, and finally 1 electron in the fourth level. Hence, the representation of potassium's electronic configuration as 2, 8, 8, 1 is accurate. The other choices do not accurately reflect the total of 19 electrons present in a neutral potassium atom. For example, the option stating 2, 8, 8, 2 suggests there are too many electrons in the neutral state, while options indicating 2, 7, 2 or 2,